1. Field of the Invention
The present invention relates to an auxiliary filtration system and a method of continuous filtration in engine applications.
2. Background Art
Current oil filtration systems for vehicle engines consist of a full flow filter in which 100% of the engine oil flow passes through the filter. The filter is designed to remove only the large particles from the oil because the filter must not restrict the oil flow. In turn, the filtering effectiveness is extremely limited. Current full flow filters are only efficient in controlling particles fifteen microns and larger. Ninety-five percent of the contamination generated within a vehicle engine is smaller then ten microns. This current filtration technology leads to short oil change intervals. Frequent oil changes are expensive, time consuming, and generate a tremendous amount of waste from the disposal of oil and oil filters. Most full flow filters are also equipped with a bypass valve. These filters have a tendency to clog before the service interval is up. When this happens, the bypass valve opens and unfiltered oil is circulated throughout the engine.
To add to the dilemma, increasingly stringent air emission regulations have dictated new engine designs employing the use of exhaust gas re-circulation (EGR) technology. EGR systems send a portion of the engine exhaust gas back to the combustion chamber in order to reduce NOx formation; however, EGR causes an increase in the amount of soot being deposited to the oil. Soot is a by-product of the combustion process and its primary component is carbon. These soot particles are very small; they are hard, abrasive and have a tendency to bind or stick together to form larger masses of soot. High soot levels in the engine oil will cause an increase in the oil viscosity, which then leads to higher operating temperatures. High soot levels will also result in the early depletion of the chemical additives in the oil which prevent oil deterioration. This leads to excessive engine wear and reduction in engine life. Finally, the large masses of soot can cause premature filter plugging. EGR provides a multi-pass opportunity for soot to enter the oil. Because of the new engine designs, especially the trend to use EGR in diesel engines, the oil is getting dirtier faster.
The industry's solution thus far has been the adaptation of bypass filter systems. The bypass filter system is typically installed in parallel to the full flow filter. The bypass filter continuously diverts a side stream of ten to fifteen percent of the engine oil flow, filters it more efficiently through the use of finer filtration, and then returns the oil back to the oil pan. The bypass filter works in conjunction with the full flow filter to capture particles and contamination that are missed by the full flow filter. When the full flow filters are run in parallel with the bypass filters, they have less work to do, thereby increasing the time between service intervals. However, the bypass filters do have limitations. Current bypass filters can capture particles in the range of five to twenty microns. This leaves many smaller and more abrasive particles suspended in the oil. One particularly harmful contaminant that remains unfiltered is soot. Soot particles are typically less than one micron in size and have a tendency to stick together or agglomerate over time. Soot agglomerates grow in size until they fall out of suspension and form sludge in the bottom of the oil pan. Because of the limited filtering capacity associated with the canister designs of current bypass filters, sludge causes premature clogging of both the full flow and bypass filters. With more soot being deposited in the oil due to EGR, this becomes an even greater concern. One final problem associated with bypass filter systems is the introduction of lube pressure parasitic losses. Because bypass systems divert approximately ten percent of an engine's total oil stream to the bypass filter, a lube pressure parasitic loss is introduced. In extreme conditions, diversion of this amount of oil can lead to starvation of necessary lubrication in certain engine components.
The use of a high efficiency bypass filtration system is not a complete answer to the problems that plague the industry. In order to extend oil and filter life, it is necessary to adopt a system that incorporates the advantages of a by-pass system with the ability to extend oil filtering capacity.